Bug using union

[yanmendes]

I have added my own data to BigDAWG, however, it's not processing unions correctly.

Issuing query via BigDAWG's interface:

curl --request POST \
  --url http://localhost:8080/bigdawg/query \
  --header 'content-type: application/json' \
  --data 'bdrel(
  select
    *
  from
    (
      select
        duration::char
      from
        (
          SELECT
            app_exec_id as execution_id,
            start_time as prov_startedAtTime,
            script_run_id as provone_hadPlan,
            duration
          FROM
            app_exec
        ) as table_7
    ) as t1
    union (
      select
        (prov_endedAtTime - prov_startedAtTime) :: char as d2
      from
        (
          SELECT
            af.id as execution_id,
            af.start_time as prov_startedAtTime,
            af.end_time as prov_endedAtTime,
            af.wf_exec_id as provone_wasPartOf
          FROM
            actor_fire as af
        ) as table_0
    )
)'

net.sf.jsqlparser.statement.select.SetOperationList cannot be cast to net.sf.jsqlparser.statement.select.PlainSelect

If you need a reproducible environment, just follow the installation steps here